THE anthropologist Napoleon A. Chagnon has spent decades studying patterns of conflict and revenge among Yanomami Indians, deep within the Amazon Basin. He needn't have traveled so far to pursue his research. After all, anthropologists themselves are one of the most bellicose tribes on earth. The discipline's latest outbreak of infighting — over accusations of "ethnographic cleansing" made against Mr. Chagnon in an upcoming book, "Darkness in El Dorado" — may be its nastiest battle yet.

Disputes within anthropology have a way of becoming blood feuds. Virtually all of the field's leading figures have been struck by poison arrows. Margaret Mead? Dupe! Franz Boas? Spy! Colin Turnbull? Hoaxer! Marshall Sahlins? Imperialist! Indeed, the excessive ferocity of anthropological warfare has fractured the discipline and tarnished its public image. It's become the academic equivalent of "The Jerry Springer Show."

Anthropology wasn't always so fratricidal. When the discipline was born 100 years ago, scholars agreed that they could observe foreign cultures, learn their customs, explicate their rituals and, in some deep way, understand them.

That faith has eroded badly. Today, the ethnographic enterprise is considered by many anthropologists to be an act of smug colonialism. How can one Westerner, they ask, possibly interpret an entire culture?

Mr. Chagnon, author of the best-selling 1968 study "Yanomami: A Fierce People," has long been criticized by his peers for just these kind of sweeping interpretations. Mr. Chagnon contends that his detailed observations of Yanomami violence offer proof that human nature is inherently antagonistic. His opponents, in turn, have accused him of turning the Yanomami into cartoons of Stone Age savagery.

"Darkness in El Dorado," by a journalist, Patrick Tierney, which was excerpted last week in The New Yorker and will be published by W. W. Norton in November, takes up the cause of Mr. Chagnon's academic enemies with a vengeance. It accuses him of cooking his data, cozying up to nefarious gold-mining interests, causing tribal conflicts by carelessly handing out machetes, pressuring Indians to break cultural taboos and faking scenes in film documentaries so exploitative that they deserve to be called snuff films.

Worse, the book suggests that Mr. Chagnon, with the late geneticist James Neel, sparked a deadly outbreak of measles among the Yanomami in 1968 through the administration of a "contraindicated" vaccine.

Mr. Chagnon and his allies have mounted a vigorous counterattack since the book's contents were described in a widely circulated e-mail written by anthropologists Leslie Sponsel and Terry Turner. (The scholars, who are major sources for the book, compared Mr. Chagnon to Josef Mengele.) After medical experts posted statements on the Internet undermining Mr. Tierney's vaccine argument, Mr. Turner last week withdrew the genocide charge.

But the broader accusation that Mr. Chagnon has slandered the Yanomami by presenting them as not-so- noble savages will not be resolved so easily — for anthropologists' judgments of Mr. Chagnon's fieldwork often have as much to do with ideology as evidence.

Anthropology is riven by two opposing worldviews. Sociobiologists, who believe that humans across the globe share an essential nature shaped by evolution, love Mr. Chagnon's work. It confirms their suspicion that men from South America to Serbia are driven by aggression. Cultural anthropologists, who emphasize the importance of local context and recoil at universal statements about human behavior, think Mr. Chagnon's conclusions are pure fantasy.

Steven Pinker, a sociobiologist who teaches cognitive science at M.I.T., liberally cites Mr. Chagnon's work in his book "How the Mind Works." "Chagnon is a great empiricist." he says. "Sadly, most anthropology is off the scale in post modernist lunacy. There's this orthodoxy that says human nature is a blank slate. For telling it like it is, he has become public enemy No. 1."

John Tooby, a colleague of Mr. Chagnon's, agrees. "Anthropologists are trained to appreciate cultural differences, but they can't stand it within their own profession," he says. "Nap is being attacked for his ideas, not because of any wrongdoing."

Cultural anthropologists admit that Mr. Chagnon is unpopular. "He is not liked," says Nancy Scheper- Hughes of the University of California at Berkeley. "He is a proponent of a view of human behavior that is very much marginalized, and for good reason."

Her colleague at Berkeley, Paul Rabinow, said: "I don't know anybody who takes him seriously. But that doesn't mean he isn't important. He's had a big popular impact."

This impact, his critics say, has been disastrous for the Yanomami, whose jungle population of 27,000 continues to dwindle. The French anthropologist Jacques Lizot says that Mr. Chagnon's tales of the Yanomami's brutish ways are used by logging and mining companies as justification for the slaughter of Indians. (In 1993, gold miners massacred Yanomami in a Venezuelan village.)

Mr. Pinker, for one, doesn't buy this argument. "There's this idea that because indigenous people have been exploited, you need to depict them as living like a hippie commune, all nice and lovable. That's crazy logic! Surely they have a right to exist whether they're nice guys or not." It's a point that threatens to get lost amid all the scholarly shouting.

What also has been lost is a sense of anthropology's original mission. As Mr. Rabinow puts it: "The idea of someone going to the most technologically simple societies and trying to learn lessons about human nature by studying them, that's been refuted."

To simply observe a threatened culture, as Mr. Chagnon did, is now considered irresponsible; the anthropologist needs to be first and foremost an activist. Indeed, Ms. Scheper-Hughes says that anthropologists these days are more concerned with "critiquing globalization" than studying local traditions.

"A graduate student here at Berkeley recently turned in a classic and beautiful ethnography about this village in Sierra Leone, about domestic rituals and notions of secrecy," she says. "But a lot of my colleagues found it wanting, because it wasn't going to help those people getting their arms chopped off! So she has to go back and rewrite it."